Crystal oscillation devices have been widely used for oscillators and the like. For example, Patent Document 1 described below discloses a crystal oscillation device in which a crystal resonator is mounted on a package board. In this example, an IC chip is fixed to a lower surface of the package board. A second board is laminated on the lower surface of the package board so as to surround the IC chip. The second board has a planar shape obtained by eliminating one side from a rectangular frame shape.
Meanwhile, in the crystal oscillation device disclosed in Patent Document 2 described below, a crystal resonator is mounted on a package board. A first leg portion and a second leg portion are provided on a lower surface of the package board at an interval. An electronic component element is fixed to the lower surface of the package board and between the first leg portion and the second leg portion.
In Patent Document 3 described below, an electronic component chip is fixed to a lower surface of a package in which a crystal resonator is housed. A metal bump joined to a lower surface of a package board is provided on an outer side portion of the electronic component chip.
Patent Document 4 described below discloses a structure in which a package in which a crystal unit is housed and a mounting board on which an IC chip is mounted are joined to each other via a bump.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-32456.
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-20633.
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2003-318653.
Patent Document 4: Japanese Unexamined Patent Application Publication No. 2010-87726.
In Patent Documents 1 to 3, the board or the leg portion provided to surround the electronic component element (such as an IC chip) is not present in a portion of a surrounding area of the electronic component such as an IC chip. Moreover, when heat is transmitted from the package board or the surrounding circuit element to the package board, the temperature of the electronic component element (such as an IC chip) easily increases. In a structure in which an IC chip including a temperature sensor is combined with a crystal resonator, when the temperature of the IC chip increases, frequency correction is performed by the included temperature sensor. Therefore, there is a problem that when the temperature of a surrounding area of the IC chip changes earlier than the temperature of a surrounding area of a crystal unit, a frequency shift will occur.